This invention relates to the use of air to air heat recovery ventilators to obtain thermally efficient ventilation of buildings and dwellings, and in particular, to a rotary wheel heat exchanger for room ventilators.
Heat exchangers are used in ventilation systems installed in residential, commercial and industrial buildings to extract and remove heat or moisture from one air stream and transfer the heat or moisture to a second air stream. In particular, rotary wheel heat exchangers are known wherein a wheel rotates in a housing through countervailing streams of exhaust and fresh air, in the winter extracting heat and moisture from the exhaust stream and transferring it to the fresh air stream. In the summer rotary wheel heat exchangers extract heat and moisture from the fresh air stream and transfer it to the exhaust stream, preserving building air conditioning while providing desired ventilation.
Fans or blowers typically are used to create pressures necessary for the countervailing streams of exhaust and fresh air to pass through the rotary wheel heat exchanger. Various media have been developed for use in rotary wheel heat exchangers to enhance heat and moisture transfer, for example, Marron et al, U.S. Pat. No. 4,093,435. Typical of rotary wheel heat exchangers are the devices shown by Hajicek, U.S. Pat. No. 4,497,361, Honmann, U.S. Pat. No. 4,596,284, and those used by Mitani, U.S. Pat. No. 4,426,853, and Coellner, U.S. Pat. No. 4,594,860, in air conditioning systems.
It has been found in the prior art that to achieve thermally efficient ventilation of rooms and buildings, rotary wheel heat exchangers require installation in rather large, fixed, or non-portable heat recouperators, such as that disclosed by Pennington, U.S. Pat. No. 2,807,258. The need exists, therefore, for smaller, portable heat exchangers and heat recovery ventilators which can still achieve thermally efficient ventilation. Further, the need exists for compact heat exchangers and heat recovery ventilators which may be used without the necessity of building modification, and may connect to existing ductwork in residential, commercial and industrial environments. This need is illustrated, for example, by the devices of Tengesdal, U.S. Pat. No. 4,688,626, Zenker, U.S. Pat. No. 4,491,171, and Berner, U.S. Pat. No. 4,542,782. Finally, the need remains for improved heat exchanger media for rotary wheel heat exchangers to increase the efficiency of heat transfer between the countervailing air streams.
Typically heat recovery apparatuses in the prior art employ heat exchangers having a plurality of parallel passages running in the direction of flow, as in Marron et al, U.S. Pat. No. 4,093,435 and Coellner, U.S. Pat. No. 4,594,860. Such passages must be sufficiently small to maximize the total surface area for heat transfer, yet sufficiently large relative to their length to minimize resistance to gas flow. These constraints have made the materials used as the heat exchanger media critical to the effectiveness of such rotary wheel heat exchangers. Thus, for example, Marron et al, U.S. Pat. No. 4,093,435, disclose the use of corrugated paper of a specified composition, density, and thickness in a plurality of layers in a rotary wheel heat exchanger. Further combination with metal foil in a multi-layered material is disclosed. Coellner, U.S. Pat. No. 4,594,860, discloses the use of sheets of polymer film alternating with layers of corrugated or extruded polymer film or tubes, each layer having specified thermal conductivity and specific heat characteristics.
In addition to ordinary ventilation requirements of residential, commercial, and industrial buildings, the increasing importance of ventilation in residences due to the hazardous build-up of radon, formaldehydes, carbon dioxide and other pollutants presents a further need for inexpensive portable, compact, efficient heat recovery ventilators which are capable of window-mounting. A continuing need exists for the improved design of rotary wheel heat exchangers, including improved, efficient heat exchanger media which avoid the exacting material and design restrictions found in the prior art.